How to make a Relay Board

Relay is a switch that can be actuated using an electrical signal. In this blog, we will discuss the operation of a relay and relay board along with the process of interfacing with different microcontrollers. There are many types of relays. We will discuss SPDT type. An SPDT relay has five terminals Normally Open (NO), Normally Close (NC), Common (C), A1 and A2 are used to power the coil. When the coil is powered contact between C and NC switches to NO side, this is called actuated state. 

Relays are used when we are using electrically isolated circuits. Like using a 5V DC Relay we can turn on 230V AC load. 

Things we need

• SPDT Relay 5V (RL1)
• NPN Transistor : BC547 (Q1)
• Resistor : 1k Ohm (R1)
• Diode : 1N4007 (D1)
• LED Optional

In our project we can connect any micronontroller's pin at Input. 1k Ohm resistor is used to control the base current of the transistor Q1. D1 is a Freewheeling Diode. RL1 is the relay that is controlling the 12V Load.

Video: